Industrial gas turbine engines often have a rotor with a first stage turbine rotor blade and a stator with a first stage stator vane located downstream from a combustor A seal is typically positioned between the stator and the adjacent rotor to form a seal for a rim cavity that exists between the stator and rotor. Purge air is provided to the rim cavity via a bypass channel and via leakage past the seal A major problem with this structure is that the seal wears, and thus the leakage flow increases The discharge through the bypass channel is constant as long as the supply pressure remains the same. Thus, as the leakage flow across the seals increases, the cooling air from both pathways into the rim cavity, past the seal and from the bypass channel, increases A need thus exists to account for seal wear and extra leakage flow into the rim cavity so that the total cooling air flow to the rim cavity is not excessive